Fixes from trial guide testing

* Heritrix.java
    fail-fast with helpful error message if launched with Java < 1.6
* EditRepresentation.java
    "save changes" rather than "update content"
* EngineApplication.java
    customize restlet error to include back-button and full stack (instead of link to HTTP spec!)

engine/src/main/java/org/archive/crawler/Heritrix.java

@@ -188,6 +188,17 @@ public class Heritrix {
     
     public void instanceMain(String[] args)
     throws Exception {
+        
+        // ensure using java 1.6+ before hitting a later cryptic error
+        String version = System.getProperty("java.version");
+        float floatVersion = Float.valueOf(version.substring(0,version.indexOf('.',2)));
+        if(floatVersion<1.6) {
+            System.err.println("Heritrix (as of version 3) requires Java 1.6 or higher.");
+            System.err.println("You attempted to launch with: "+version);
+            System.err.println("Please try again with a later Java.");
+            System.exit(1);
+        }
+        
         // Set some system properties early.
         // Can't use class names here without loading them.
         String ignoredSchemes = "org.archive.net.UURIFactory.ignored-schemes";

engine/src/main/java/org/archive/crawler/restlet/EditRepresentation.java

@@ -63,7 +63,8 @@ public class EditRepresentation extends CharacterRepresentation {
         PrintWriter pw = new PrintWriter(writer); 
         Flash.renderFlashesHTML(pw, dirResource.getRequest());
         pw.println("<form method='POST'>");
-        pw.println("<input type='submit' value='update contents'/>");
+        // TODO: enable button on after changes made
+        pw.println("<input type='submit' value='save changes'/>");
         pw.println(fileRepresentation.getFile());
         Reference viewRef = dirResource.getRequest().getOriginalRef().clone(); 
         viewRef.setQuery(null);

engine/src/main/java/org/archive/crawler/restlet/EngineApplication.java

@@ -20,6 +20,8 @@
 package org.archive.crawler.restlet;
 
 import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringWriter;
 
 import org.archive.crawler.framework.Engine;
 import org.archive.util.TextUtils;
@@ -31,6 +33,11 @@ import org.restlet.Router;
 import org.restlet.data.MediaType;
 import org.restlet.data.Reference;
 import org.restlet.data.Request;
+import org.restlet.data.Response;
+import org.restlet.data.Status;
+import org.restlet.resource.Representation;
+import org.restlet.resource.StringRepresentation;
+import org.restlet.service.StatusService;
 import org.restlet.util.Template;
 
 /**
@@ -46,6 +53,7 @@ public class EngineApplication extends Application {
         this.engine = engine;
         getMetadataService().addExtension("log", MediaType.TEXT_PLAIN );
         getMetadataService().addExtension("cxml", MediaType.APPLICATION_XML );
+        setStatusService(new EngineStatusService());
     }
 
      public synchronized Restlet createRoot() {
@@ -95,4 +103,32 @@ public class EngineApplication extends Application {
     public Engine getEngine() {
         return engine;
     }  
+    
+    /**
+     * Customize Restlet error to include back button and full stack.
+     */
+    protected class EngineStatusService extends StatusService {
+
+        @Override
+        public Representation getRepresentation(Status status, Request request, Response response) {
+            StringWriter st = new StringWriter();
+            PrintWriter pw = new PrintWriter(st);
+            pw.append("<h1>An error occured</h1>\n");
+            pw.append(
+                "You may be able to recover and try something " +
+                "else by going <a href='javascript:history.back();void(0);'>" +
+                "back</a>.\n");
+            if(status.getThrowable()!=null) {
+                pw.append("<h2>Cause: "+
+                    status.getThrowable().toString()+"</h2>\n");
+                pw.append("<pre>");
+                status.getThrowable().printStackTrace(pw);
+                pw.append("</pre>");
+            }
+            pw.flush();
+            return new StringRepresentation(st.toString(),MediaType.TEXT_HTML);
+        }
+
+    }
+
 }